A United Nations-proposed pause in the fighting in the Syrian ciy of Aleppo to allow for humanitarian aid "is not going to happen", an expert in the region has told talkRADIO.

The UN is calling for a postponement of hostilities to allow aid workers to repair water supplies in the beseiged city, which has been the scene of renewed fighting in recent days. The organisation says there are up to two million people in the area without water.

At least 250,000 people are reported to be trapped in eastern rebel-held areas of Aleppo, after the government cut off a key route into the area in July. On Sunday, rebel forces responded by cutting off a major access route into the west of the city.

Tim Eaton, who is the project manager for the Syria and Its Neighbours Policy Initiative with the Royal Institute of International Affairs, updated talkRADIO's Sam Delaney on the latest twist in the long-running conflict.

"[The pause] is not going to happen," he said. "The UN has been consistent in seeking pauses. There's no end in sight [to the fight] at present.

"The situation is incredibly fluid and confused.

“The events of recent days have essentially made it that the east is being laid siege to by the regime, and the west is being laid siege to by the rebels.

“It’s strike and counter-strike in Syria, without one side being able to deliver a telling blow.”